Circuit breaker with heat pipe cooling means

ABSTRACT

A multi-phase electric circuit control device mounted in a switchboard includes a heat pipe for each phase, having one end in close thermal contact with a relatively high-temperature point of the control device and extending behind the device. The heat pipe has heat-dissipating fins positioned in a portion of the switchboard where natural circulation of the air serves to carry heat away and thereby dissipate heat from the high-temperature point of the control device, making it possible for the control device to carry more current than it would otherwise be able to do safely. In one form, heat is drawn from a point intermediate to the ends of the control device by a heat pipe and heat transfer means extending through an opening in the back wall of the casing of the device. In another form, the heat pipe transfers heat away from the circuit control device terminals.

te S13E68 Patent [1 1 Corman et a1.

[ CIRCUIT BREAKER WITH HEAT PIPE COOLING MEANS [75] Inventors: James Corman, Scotia; Gunnar E.

Walmet, Schenectady; Stanley P. Urbaetis, Mechanicville, all of N.Y.; Herbert M. Dimond, West Hartford, Conn.

[7 3] Assignee: General Electric Company, New

York, NY.

[22] Filed: Aug. 14, 1972 [21] Appl. No.: 280,228

12/1971 Sturdivan 317/120 Oct. 30, 1973 3,349,291 10/1967 Olashaw .3l7/l2O Primary Examiner-Robert K. Schaefer Assistant Examiner-Gerald P. Tolin Attorney-Robert T. Casey et al.

[57] ABSTRACT A multi-phase electric circuit control device mounted in a switchboard includes a heat pipe for each phase, having one end in close thermal contact with a relatively high-temperature point of the control device and extending behind the device. The heat pipe has heat-dissipating fins positioned in a portion of the switchboard where natural circulation of the air serves to carry heat away and thereby dissipate heat from the high-temperature point of the control device, making it possible for the control device to carry more current than it would otherwise be able to do safely. 1n one form, heat is drawn from a point intermediate to the ends of the control device by a heat pipe and heat transfer means extending through an opening in the back wall of the casing of the device. In another form, the heat pipe transfers heat away from the circuit control device terminals.

4 Claims, 7 Drawing Figures PAIENIEnncrso ms v 3.769.551

' sum 1 or 3 /IN5ULATION INSULATION/J BACKGROUND OF THE INVENTION Electric Circuit control devices, such as electric switches and circuit breakers, are limited as to the amount of current they can normally carry by thefpermissible temperature rise caused by such current, usually measured at the terminals of the device. Although usual test procedures call for testing of the temperature rise at the terminals of the device, excessive temperature rise at other points inside the device also impose practical limitations on their designs such as by causing deterioration of metallic and/or insulation materials in the device.

Such temperature rise is of particular concern in devices such as molded case switches and circuit breakers, which have most of their operating and current conducting parts contained within a closed box or casing which does not permit free circulation of air which would help dissipate such heat. Such heat rise problems are also of particular concern in assemblies such as switchboards and panelboards, wherein such devicesare mounted within another enclosure, which may-fun ther inhibit cooling of the device.

Because of such problems, it has been necessary in the prior art to impose limitations on the amount of current which can be carried by such devices. For example, it is commonly required to derate a control device if "and when it is to be used in an electrical control apparatus assembly which includes a number of such devices positioned relatively close together. Thus a IOO-ampere circuit breaker may be limited to carrying not more than 80 amperes when so used. In addition, when relatively high current capacity devices which are of the totally enclosed type, such as molded case circuit breakers, are desired, it has been necessary to provide relatively large, heavy masses of conductive metal to reduce the electrical resistance-in the device and also to act as a heat'transfer means. The use of such large masses of conductive material is expensive, and adds to the size and weight of the devices.

OBJECTS OF THE INVENTION It is an object of the invention to provide an electric circuit control device of the type suitable for use in electric switchboard or panelboard assemblies, including novel heat-dissipating means, permitting a substantial increase in the permissible current carrying rating of the device or, conversely, substantial reduction of the amount of current carrying metallic materialrequired in the device.

It is a further object of the invention to provide an electric circuit control device for assembly in an electric switchboard or panelboard having effective heatdissipating means as described, without requiring major redesign or rearrangement of the component-parts of the control device.

It is another object of the invention to provide an electric circuit control device including novel heatdissipating means as described,.which shall not require major modification of the switchboard, panelboard, or other electrical control apparatus assembly in which it may be mounted.

It is a further object of the invention to provide. an electric circuit control device including novel and effective heat-dissipating means as described which does not require any greater space in a switchboard or panelboard assembly in which it is used than a comparable prior art control device without such heat-dissipating means.

It is a further object of the invention to provide an electric circuit control device including novel heatdissipating means as described which does not require any moving parts for the heat-dissipating function.

SUMMARY OF THE INVENTION In accordance with the invention in one form, an electrical control apparatus assembly is provided including an electric circuit control device such as an electric switch or circuit breaker of the type adapted to be mounted in electric switchboard or panelboard, and an elongated vaporizingcondensing heat pipe heattransporting device positioned with the heat-receiving (evaporating) end thereof in close thermal contact with a relatively high-temperature point of the circuit control device and extending generally away from the device, together with heat dissipating fins disposed along the length of the heat pipe to enhance the dissipation of heat from the device. In a particular form of the invention, the heat-receiving end of the heat pipe is in close thermal contact with an internal portion of the circuit control device between the ends of the device, and projects from the back wall of the device. In another form of the invention the heat receiving end of theheat pipe is in close thermal contact with a terminal portion of the circuit control device.

As used hereinjthe term heat pipe refers generally to a heat-transfer and/or dissipating device comprising a hermetically sealed enclosure having a quantity of vaporizable liquid therein and having a first portion where evaporation of the liquid to vapor form normally occurs to absorb heat and a second portion where condensation of the vapor normally occurs to give up heat.

Further, in accordance with the invention, a multipole circuit control device is provided, having at least one heat pipe heat-dissipating means for each pole of the multipole device.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary side elevation view of an electric circuit control device in mounted position in an electric power switchboard;

FIG. 2 is a sectional view of the apparatus of FIG. 1, taken on a plane generally indicated by the line 2-2 of FIG. 1;

FIG. 3 is an exploded fragmentary view of a portion of the invention shown in FIG. 1;

FIG. 4 is a view, partially in section, showing the construction ofa heat pipe heat transporting device as used in the invention;

' FIG. 5 is a fragmentary view of a modified form of the invention;

FIG. 6 is a side elevation view, on reduced scale, of

another embodiment of the invention, and

FIG. 7 is a fragmentary view of another embodiment of the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIGS. 1 through 4, the invention is shown as incorporated in an electric circuit control device indicated generally at 10, mounted in an electric switchboard, shown only partially and indicated generally at 11. In the illustrated embodiment, a molded-case electric circuit breaker is shown. It will be understood,

however, that the invention may be utilized with other electrical control devices, such as electric switches. For purposes of illustration, the invention is shown as used in connection with a molded-case type electric circuit breaker of the general type shown in US. Pat. No. 3,365,561, issued Jan. 23, 1968, to C. L. Jencks and G. W. Kiesel, and assigned to thesame. assignee as the present invention. Reference may also be had to the following patents, also assigned to the same assignee as the present invention, showing examples of a large number of electric circuit control devices with which the invention may be used: US. Pat. Nos. 3,263,051 Gauthier,'et al., July 26, 1966; 3,343,109 Jencks, et a1., Sept. 19, 1967-, 3,141,934 Beaudoin, et al., July 21, 1964; 3,243,559 Heft, March 29, 1966.

The switchboarcl section 11 comprisesa generally rectangular vertically extending cubicle including .a back wall 12 which may be removably mounted, by suitable means such as by bolts 13, and opposed side walls 14. A front wall 15 is also provided which also may be removably mounted by suitable means, such as by bolts 16. A generally sheet-like member of insulating material 17 is also provided which is supported between the sidewalls 14, by suitable means, such as by b'racketsl8. A second insulating sheet member 19 is also provided which is mounted between the side walls 14 by suitable means, such as by brackets 20.

The switchboard cubicle 11 also includes incoming power supply bus bars 22, supported therein by suitable means, not shown. Outgoing or load bus bars 24 are also provided (only one shown) supported in the switchboard cubicle also by suitable means, not shown.

The electric circuit control device is a three-pole device, i.e., it has three current paths therethrough and three sets of cooperating contacts, to be described, one

set being located ,in each path or pole. Accordingly, the switchboard section 11 includes three incoming power supply bus bars 22, and three outgoing load bus bars 24'.-The insulating sheet 19 is provided for the purpose of shielding the incoming or power supply bus bars 22 from the back when the removable back cover 12 is removed. The-insulating sheet member 17 is provided for the purpose of supporting the electric circuit control devices, such as 10, and also for shielding the incoming power supply bus bars 22 when the removable front cover is removed.

The circuit control device 10 is mounted on the insulating support sheet 11 by suitable means, such as by two sets of mounting bolts 26, 27 which pass through holes in the insulating support sheet. 17 and into threaded engagement with tapped inserts which are molded into the back wall of the molded-case circuit breaker 10. The control device is also retained in place by its connecting means to the bus bars 22 and 24.

The circuit control devicelO includes three line terminals 28 in the form of a pair of spaced projecting flat conductive members, and a set of three load terminals 29 also in the form, of pairs of spaced flat conductive members. The line terminals 28 are bolted to the in-' coming power supply bus bars 22 by means of bolts 30,

in turn is pivotally supported, at 37 on the contact pivot block 38.

It will be understood that the electric circuit control device 10 includes manual operating means for operating the contacts 34 and 35 between Open and Closed position, and also automatic current responsive means for automatically opening the contacts upon the occurrence of excess current conditions, all in accordance with prior art molded-case electric circuit breakers. In FIG. 1, such operating means is only partially shown, as'including toggle links 40 and 41, and operating handle 42. The current responsive trip member assembly or trip unit" is indicated generally at 44. The toggle links 40, 41 are operated by an overcenter spring, such as by spring 45.

The current path through any given pole of the circuit breaker 10 is therefore as follows: From the supply bus bar 22 to the terminals 28, to the stationary contact 34, to the movable contact 35, to the pivot block 38, to the trip unit 44, to'the out-going or load terminals 29, to the load terminal bus bars 24.

It will be understood that the form of the operating mechanism may vary considerably, and there may be an operating mechanism for each of the poles of the circuit breakers, etc., although in any case, all movable contact members would be operated simultaneously by g the operating handle 42 and opened simultaneously by the current responsive trip means.

' Although only asingle movable contact member 35 has been shown and described, the circuit control device 10 includes a plurality of such movable contact .members for each pole, and the pivot'block 38 includes a pivot support means for each of the movable contact members 35 for that particular pole, all as set forth and described in greater detail in the aforesaid US. Pat. No. 3,365,561. The movable contact member 35 of the present application corresponds to the movable contact member 26 of the aforesaid patent, and the pivot block 38 of the present application, corresponds to the pivot block 22 of the aforesaidpatent.

In accordance with the present invention, heat .is taken out of the center of the circuit control device 10 and dissipated effectively in the ambient air. For-this purpose, the pivot block 38 is formed with an integral generally cylindrical projection 38A, see FIG. 3, having a tapped hole 38B therein. In addition, the back wall of the circuit breaker casing 10C has an opening 10A formed therein, and the insulating support plate 17 has a corresponding opening 17A.

For the purpose of extracting heat from the pivot block 38 of each of the poles of the circuit control device 10, heat pipe assemblies are provided, indicated generally at 50. Each heat pipe assembly 50 has one end in close thermal contact with one of the pivot blocks 38 in a manner to be described, through an opening 10A in the back wall of the casing 10C. Each heat pipe assembly 50 includes a heat-spreader block 51, having a threaded projecting stud 52. The heat pipe proper comprises an elongated tubular member 53, having a reduced tubular evacuating member 54, by which the interior of the heat pipe may be evacuated and then sealed as by pinching or otherwise closing the tubular member 54. The heat pipe assembly 50 also includes a wick lining member 55, which may be of any suitable material, such, for example, as wire screening material. The tubular member 53 also contains a small amount of a vaporizable liquid, such as mate thermal contact with the tube 53..

water 56. The wick lining 55 extends to the end of the heat-spreader block 51.

For the purpose of dissipating heat from the tubular member 53 to the surrounding ambient air, a series of circular fin members 57 are provided whichare in inti- In theory and operation, the heat pipe assembly 50 is similar to the heat pipe members shown and described in the following prior art publications:

How Heat Pipes Work Daniel B. Dallas, ASTME Vectors. 1968/3 U.S. Pat. No. 2,350,348 R. S. Gaugler, June 6, 1944 U.S. Pat. No. 2,779,143 H. B. Brooks, Jan. 29, 1957.

Each heat pipe assembly 50 is mounted by threaded engagement of the stud portion 52 in the tapped hole 38B. Thus the heat pipe members are carried by the control device 10.

It will be understood that the particular form and construction of the heat pipe assembly 50 may be varied as desired.

The operation of the heat pipe assembly 50 is as follows. Heat in the pivot block 38 is conducted to the projection 38A and further, to the spreader block 51 of the heat pipe assembly 50. Heat is the block 51 is transmitted through the walls of the tubular member 50 at the left hand end as viewed, and raises the temperature of the working fluid 56, causing it to be evaporated. The fluid vapor fills the remaining space in the tube 53, and when it contacts relatively cooler surface portions, such as any portion spaced away from the block 51, is condensed into liquid. The liquid 56 absorbs a relatively large quantity of heat when changing from a liquid to a vapor. This amount of heat is known as the heat of vaporization. This heat is given up at the remote location when the vapor condenses. The fins 57 serve to keep the remaining portion of the tubular member 53 cool by facilitating the transfer of heat from it to the surrounding air.

It will be observed that the heat pipe member 50 is positioned so that the fin bearing portions of it are in the vertically extending'open spaces of the switchboard between the bartiers l7 and 19, and between 19 and the back wall 12. Thus the natural tendency of air to circulate by rising whenheated is utilized to enhance the dissipation of heat. As illustrated, the heat pipe members 50 preferably extend upwardly from the back wall of the casing of the device 10. An angle greater than 7 is preferred. This facilitates thereturn of condensed liquid to the lower or left-hand end of the heat pipe. If desired, however, the heat pipe may be horizontal. In this case, wicking" would be used the full length of the pipe, to return liquid to the left or evaporating end, by capillary action.

It will be observed that by positioning the heat pipe, heat-transfer and dissipating means at a point intermediate the line and load terminals of the device, heat may be drawn from both of the end regions of the circuit control device 10, and therefore only three such heat pipe heat-dissipating members may be required for a three-pole circuit breaker, rather than six, in,

order to keep the temperature of both line and load terminals below a predetermined level.

In FIG. 5 there is illustrated an embodiment in which the wall 12 of the main enclosure is also used as a radiating surface. For this purpose, a heat lbleeder block 6 12A of suitable metallic is attached to the end of each heat pipe 50 and the wall 12 abuts against the back surface 12A of the block 12A. Since the heat pipe 50 is at the electric potential of its associated circuit breakerpole, the heat pipe is insulated from the block 12A by suitable means, such as by having the end of the heat pipe coated with a thin tough coating 53A of insulating material.

In FIG. 6 the invention is shown as including heat pipe assemblies 150 each mounted on an angular extension of the plate 101 which supports the corresponding stationary contact 102 of the control device 110. 1

In this form, the heat pipe assemblies extend vertically, and include disc-shaped fin members 157. In the alternative, vertically-extending fin members may be used, as illustrated at in FIG. 7.

It will be readily apparent that many modifications of the invention may be made by those skilled in the art. Thus, for example, the heat pipe members may project from any other desired surface of the causing of the device 10, such as from the side walls, the end walls, or the front surface. Also, the form of the fins 57 may vary greatly, or insome cases, be omitted entirely, since the surface of the pipe 53 acts as a heat radiator. It is therefore intended, by the appended claims, to cover all such modifications as fall within the true spirit and scope of the invention.

We claim:

1. For use within a closely surrounding enclosure such as a box or electric switchboard, a multi-pole electrical control device comprising:

a. a generally rectangular housing;

b. a plurality of line terminals adjacent one end of said housing, there being at least one such terminal for each pole of said device;

c. a plurality of load terminals adjacent the other end of said housing, there being at least one such terminal for each pole of said device;

d. heat transfer and dissipating means carried by said device, said heat transfer and dissipating means I comprising at least one metallic member carried by said enclosure independent of and intermediate said terminals;

e.'said heat transfer and dissipating means also comprising at least one elongated heat pipe member fixedly attached to and supported entirely by said control device in good thermally conductive contact with said metallic member;

. said control device housing having a front wall and an operating handle member projecting from said front wall;

g. said control device having a back wall generally parallel to and spaced from said front wall;

h. the combination of said metallic member and said heat pipe member extending through an opening in said back wall of said housing intermediate said ends of said housing;

i. a plurality of heat dissipating fins carried by said heat pipe at least adjacent the end thereof remote from said back wall of said control device, whereby heat absorbed by said metallic member when said control device is in use is transferred away from said control device and dissipated to circumambi- .ent air at a location spaced away from said control device.

4. An electrical control device as set forth in claim 1 wherein said device includes a metallic member for each pole of said device and wherein said device further includes a heat pipe member and heat dissipating means associated with each of said metallic members and wherein said heat pipe members each external a substantial distance farther away from said back wall of said housing than said terminals. 

1. For use within a closely surrounding enclosuRe such as a box or electric switchboard, a multi-pole electrical control device comprising: a. a generally rectangular housing; b. a plurality of line terminals adjacent one end of said housing, there being at least one such terminal for each pole of said device; c. a plurality of load terminals adjacent the other end of said housing, there being at least one such terminal for each pole of said device; d. heat transfer and dissipating means carried by said device, said heat transfer and dissipating means comprising at least one metallic member carried by said enclosure independent of and intermediate said terminals; e. said heat transfer and dissipating means also comprising at least one elongated heat pipe member fixedly attached to and supported entirely by said control device in good thermally conductive contact with said metallic member; f. said control device housing having a front wall and an operating handle member projecting from said front wall; g said control device having a back wall generally parallel to and spaced from said front wall; h. the combination of said metallic member and said heat pipe member extending through an opening in said back wall of said housing intermediate said ends of said housing; i. a plurality of heat dissipating fins carried by said heat pipe at least adjacent the end thereof remote from said back wall of said control device, whereby heat absorbed by said metallic member when said control device is in use is transferred away from said control device and dissipated to circumambient air at a location spaced away from said control device.
 2. An electrical control device as set forth in claim 1 wherein said device includes a metallic member for each pole of said device and wherein said device further includes a heat pipe member and heat dissipating means associated with each of said metallic members.
 3. An electrical control device as set forth in claim 1 wherein said heat pipe extends a substantial distance farther away from said back wall of said control device housing than said terminals.
 4. An electrical control device as set forth in claim 1 wherein said device includes a metallic member for each pole of said device and wherein said device further includes a heat pipe member and heat dissipating means associated with each of said metallic members and wherein said heat pipe members each external a substantial distance farther away from said back wall of said housing than said terminals. 